X-ray imaging is applied in various technical fields in order to obtain information about internal structures within a region of interest of an object. For example, medical X-ray imaging devices are used to obtain information about internal structures within a patient's body. Phase contrast imaging, e.g. using an interferometer, has been developed to provide higher contrast, especially in soft tissue and other low-absorbing materials. At the same time, the interferometer may also yield a dark-field signal, related to small-angle scattering from structures smaller than the spatial resolution of the detector. The phase information may be acquired using a phase stepping method, which may require multiple exposures. For example, US 2014/0177795 A1 describes an electronic phase stepping method for acquiring the phase information.